Display systems of the kind set forth are well known. They belong to the so-called non-luminous display types, of which a well-known example is the Liquid Crystal Display device.
In these LCD devices the light modulation device consists of a pixilated panel comprising liquid crystal (LC) elements functioning as a variable transmission filter. The illumination device (also known as the backlight unit) comprises light source means. Generally, these are low-pressure mercury vapor discharge lamps. Recently, however, LED based backlight units have been described.
One of the technical challenges with electrical devices in general and display systems in particular is the minimization of the overall power consumption of the device.
Seetzen et al. describe in ‘High Dynamic Range Display Systems’ (Proceedings of ACM SIGGRAPH conference 2004) a display system based on the fundamental idea of using a ‘first display’, i.e. an LCD panel, as an optical filter with a programmable transparency to modulate a high intensity but low-resolution image from a ‘second display’. This ‘second display’ being an array of LEDs, the intensity of which can be programmed individually. Thus their display system generates a picture in accordance with image information derived from a video signal by distributing said image information over the ‘first’ and ‘second’ displays. More precisely, it is suggested that optimally the image information derived from the video signal is distributed evenly over the LCD light modulation device and the LED illumination device. This choice of a 50%/50% distribution is inspired by considerations with respect to rounding errors. A drawback of the solution described by Seetzen et al. is that the overall power consumption of the display system is still relatively high. Therefore, they do not solve the technical challenge of minimizing the overall power consumption of display systems of the kind set forth.